The paper provides choice theoretic foundations for impulsive behavior and changing taste. Similar to other studies in the literature, revelation is possible owing to self-limitation. However, in contrast to the usual unrealistic assumption that self-limitation opportunities are exogenous and observable, we follow Laibson’s classical paper by allowing for self-limitation through investing only in illiquid assets. This approach allows us to identify impulsive behavior and changing taste using only standard demand data. In addition, we provide a refinement for an individual’s welfare that is based on libertarian considerations. The refinement uniquely identifies the revealed impulsiveness in our model, and ultimately leads to a notion of comparative impulsiveness. Finally, we relate the comparative impulsiveness in our model to existing measures of (ir)rationality.